Wide angle lens

ABSTRACT

Wide angle lens having angle of view + OR - 60* or more comprises two converging lens components, with at least one cemented surface between lens elements therein, separated by a diaphragm, and two diverging menisci enclosing said components and diaphragm, the menisci concave facing the diaphragm. The convex outer surface of the component on the image side of the diaphragm faces away from the latter and has greater curvature than the preceding cemented surface. The convex side of said preceding cemented surface faces the diaphragm and has a lower refractive index on its diaphragm side than on its image side.

OR 32339;??? QEARCH ROOM [72] inventor Ludwig Bertele [56] ReferencesCited H rbmu, all. rland UNITED STATES PATENTS $5; 33 1970 v 3,154,62810/1964 Bertele 350/214 [45] Patented D. 28,3971 3,447,861 6/1969Schlegel 350/2204 [32] Priority Apr. 14, 1967 Primary Examiner-DavidSchonberg [33] Switzerland Assistant Examiner-Paul A. Sacher 31 5413/67Attorney- Baldwin, Wight & Brown Continuation-impart of application Ser.No.

719 432 Apr.8 1968 now abandoned. a ThkappuauonMu i 1970 S". No.ABSTRACT: W1de angle lens having angle of view :60 or more comprises twoconverging lens components, with at least one cemented surface betweenlens elements therein, separated by a diaphragm, and two divergingmenisci enclos- [54] WIDE ANGLE LENS ing said components and diaphragm,the menisci concave fac- 5C|gim ,3D i 1-1 ing the diaphragm. The convexouter surface of the component on the image side of the diaphragm facesaway from [52] U.S.Cl 350/2l5, the lane, and has greater curvature thanthe preceding I mented surface. The convex side of said precedingcemented [5i] lnt.C G022l;)99/ 34: Surface faces the diaphragm and has alower refractive index new surch 2 on its diaphragm side than on itsimage side.

PATENTEU UEC28 l97l SHEET 1 OF Q m m Q: Q: Q E q @HE E 2 E Q mt V? NE NEQ? M M v m W t WIDE ANGLE LENS This Application is aContinuation-in-Part of my Application No. 719,432 filed Apr. 8, i968,and now abandoned.

This invention relates to wide-angle objective lenses. and concerns sucha lens of the type which has an angular field'of :60" or more. largelyfree of distortion, the lens including two converging lens elements,each of which is composed of a plurality of individual lenses, theelements being separated by a diaphragm, and which, both on the objectside and on the image side, are enclosed by at least two divergingmenisci. the concave sides of which face the diaphragm.

According to this invention. in a wide-angle lens of the type described.the outer convex surface of the converging lens element situated behindand facing away from the diaphragm has greater curvature than thepreceding cemented surface which has its convex side facing thediaphragm, with a lower refractive index on the diaphragm side than onthe image side.

A lens according to' the invention is shown in FIG. 1 of theaccompanying drawings. l

FIG. 2 shows the astigmatic image curves, particularly the sagittalcurve, in the case of a known lens. while by way of comparison FIG. 3shows the corresponding curves for alens according to the invention. Thesolid line is the sagittal and the broken line the meridianal imagecurve.

The axial distance from the cemented surface, which is in the converginglens element and situated in front of the diaphragm and has its concaveside facing the latter, with a higher refractive index on the diaphragmside thanon the object side (see r,. in FIG. I), to the cemented surfacewhich in the converging lens element is situated behind the diaphragmand has its convex side facing the latter, with a smaller refractiveindex on the diaphragm side than on the .image side (see r, in FIG. 1 isgreater than 0.25 F and smaller than 0.37 F.

Known wide-angle objective lenses are found to lack sharpness ofdefinition at the edges of the image, since the sagittal image curve isconsiderably curved towards the lens with an angle of view above 145,even when at smaller angles of view it faces away from the lens.

Exhaustive investigations have shown that this aberration can be reducedaccording to the invention which provides a wide-angle lens in which thecemented surface. which is disposed in the converging lens elementsituated on the image side of the diaphragm, has its convex surfacefacing the latter, has a smaller refractive index on the diaphragm sidethan on the image side (r is displaced in the direction of the image tosuch a considerable extent that it is further from the diaphragm thanthe cemented surface having its concave side facing the diaphragm, andhas a radius of curvature which is greater than that of the followingconvex outer surface. This measure, however, has a considerableefl'ecton the chromatic aberrations for the different angles of view. Ithas nevertheless been found that these aberrations can be satisfactorilycorrected if the distance between the aforesaid cemented surface (r anda cemented surface, which in the converging lens element is situated infront of the diaphragm and' has its concave side facing the latter, witha higher refractive index on the diaphragm side than on the object side(r5), ranges from 0.25 F to 0.37 F.

'With such a wide angle of view it is necessary to consider the opticalpath over the full width in the sagittal section also. It is then foundthat it is advantageous for the focal length of the diverging lenselement (A) situated on the object side to be made greater than l .08 Fand smaller than l .60 F. The focal length of the diverging lens element(D) situated on the image side should moreover be greater than 0.83 Fand smaller than l.05 F. It is in addition preferable for the menisci tobe given a less sharp curvature than the known lens, so that the sum ofthe radii of curvature of the concavities in the menisci on the objectside exceeds l.l2 F. The size of the partial focal lengths and of thesum of the aforesaid radii of curvature depends on the permissibleoverall lengths of the lens and the consequent diameter of the divergingmeniscus group.

, It is also preferable that the numerical sum of the radii'of curvatyre0f the outer surfaces, facing away from the diaphragm. of the twoconverging elements is made greater than l.0 F and smaller than L50 F.

In connection with correction of distortion it has been foundadvantageous to keep the quotient of the radius of curvature of thefirst and last surfaces of the lens between l.l 0 and 2.20.

A cemented surface in the converging lens element on the 10 image sidehas its. concave surface facing the diaphragm (r,,)

and the refractive index is graduated so that it is smaller on the sidefacing the diaphragm than on the side facing away from the latter.Spherical aberration is thereby eliminated in known manner. The sameefiect can also be achieved with an uncemented surface pair separated bya small air space and with any desired graduation of the refractiveindex, if the two surfaces have different curvatures. The same is alsotrue of the corresponding cemented surface, likewise having its concaveside facing the diaphragm (r in the converging lens element on theobject side, with a smaller refractive index on the diaphragm side thanon the object side.

As compared with known lenses, the lateral chromatic aberration at theedge of the. image is considerably reduced by the 2s movement towardsthe image of the previously mentioned cemented surface (r having itsconvex side facing the diaphragm, in the converging lens element on theimage side. The measures described also permit enlargement of thediaphragm space, which is advantageous in respect of the fitting of aniris diaphragm and of a shutter diaphragm.

Three examples of lenses according to this invention will now bedescribed with reference to FIG. 1 of the accompanying drawings. Thelenses have a focal length F=l00 mm. an aperture ratio of l:5.6-, and anangle of view of l20. The two converging lens elements are designated byB and C and the two meniscus groups enclosing them are designated by Aand D. The lens element B is composed of four members L -L at least L.and L, and also L, and L being cemented. The lens element C consists ofthree members L L,, and are shaped 40 and disposed as described above.

The valuesof the radius of curvature of the cemented surface which hasits convex side facing the diaphragm (r and that of the following outersurface (r as well as the axial distance between the surfaces r and rare as follows:

In the tables set out below, the constructional data are given for threelenses constructed according to theinvention. Of course, a similarcorrection condition can also be achieved with data which are betweenthe values given.

lens element A and/or lens element D may consist of more than twomenisci.

The radii of curvature of the lens surfaces are designated by r, thethicknesses of the lenses by d, the air spaces by l. the

refractive index for the helium line by n,,, and the Abbe figures 1. Aphotogrammetric objective consisting essentially of six lens unitsseparated by air spaces, and a diaphragm positioned between the thirdand fourth lens units, the said lens units. beginning at the region ofgreater beam width, having the following arrangement and configurations:

a. a first lens unit (L and a second lens unit (L,) which are bothconstituted by diverging meniscuses convex in the direction of theobject and which are separated by an air space having the shape of aconverging meniscus;

b. a third lens unit (B) which is a converging unit composed of fourindividual lenses cemented together, these being (i) a diverging lens (Lboth surfaces convex in the direction of the object, (ii) a biconvexconverging lens (L (iii) a biconcave diverging lens (L and (iv) aconverging lens (L,,) which has its surface of substantially greaterradius of curvature on the diaphragm side, its other surface beingconvex toward the object side. and which has a higher refractive indexthan the preceding diverging lens (L c. a fourth lens unit (C) which isa converging unit disposed beyond the diaphragm and composed of threeindividual lenses cemented together, these being (i) a convex lens (L-,)which has its surface ofa substantially greater radius of curvature onthe diaphragm side and its other surface being convex on the image side,(ii) a biconcave lens (L,.) and (iii) a biconvex lens (L,,) which has ahigher refractive index than the preceding diverging lens (L,.) thecemented surface r between the biconcave lens (L and the biconvexbiconvex lens (L having a radius of curvature greater than the outersurface (r,;;) on the image side; and

d. a fifth lens unit (L and a sixth lens unit (L,,) which areconstituted by diverging meniscuses convex in the direction of the imageand which are separated by an air space having the shape of a convergingmeniscus.

2. A photogrammetric objective as claimed in claim I, wherein thedistance between that cemented surface (r,.) which is provided withinthe said third lens unit (B). is closest to the diaphragm, and isconcave in the direction of the diaphragm, and that cemented surface (rwhich is provided within the said fourth lens unit (C), and is convex inthe direction of the diaphragm. is greater than 0.25 F and less than0.37 F. i

3. A photogrammetric objective according to claim I in which the radiiof curvature r of the lens surfaces, the lens thicknesses d, the airspaces 1, the refractive indices for the helium line n,,, and the Abbefigures 11,, are substantially as set forth in the following table:

LII

5. A photogrammetric objective according to claim I in which the radiiof curvature r of the lens surfaces. the lens thicknesses d, the airspaces 1. the refractive indices for the helium line n,,, and the Abbefigures vdare substantially as set forth in the following tables:

I .65 lot]

1. A photogrammetric objective consisting essentially of six lens unitsseparated by air spaces, and a diaphragm positioned between the thirdand fourth lens units, the said lens units, beginning at the region ofgreater beam width, having the following arrangement and configurations:a. a first lens unit (L1) and a second lens unit (L2) which are bothconstituted by diverging meniscuses convex in the direction of theobject and which are separated by an air space having the shape of aconverging meniscus; b. a third lens unit (B) which is a converging unitcomposed of four individual lenses cemented together, these being (i) adiverging lens (L3) both surfaces convex in the direction of the object,(ii) a biconvex converging lens (L4), (iii) a biconcave diverging lens(L5) and (iv) a converging lens (L6) which has its surface ofsubstantially greater radius of curvature on the diaphragm side, itsother surface being conVex toward the object side, and which has ahigher refractive index than the preceding diverging lens (L5); c. afourth lens unit (C) which is a converging unit disposed beyond thediaphragm and composed of three individual lenses cemented together,these being (i) a convex lens (L7) which has its surface of asubstantially greater radius of curvature on the diaphragm side and itsother surface being convex on the image side, (ii) a biconcave lens (L8)and (iii) a biconvex lens (L9) which has a higher refractive index thanthe preceding diverging lens (L8) the cemented surface r12) between thebiconcave lens (L(90) 8) and the biconvex lens (L9) having a radius ofcurvature greater than the outer surface (r13) on the image side; and d.a fifth lens unit (L10) and a sixth lens unit (L11) which areconstituted by diverging meniscuses convex in the direction of the imageand which are separated by an air space having the shape of a convergingmeniscus.
 2. A photogrammetric objective as claimed in claim 1, whereinthe distance between that cemented surface (r8) which is provided withinthe said third lens unit (B), is closest to the diaphragm, and isconcave in the direction of the diaphragm, and that cemented surface(r12) which is provided within the said fourth lens unit (C), and isconvex in the direction of the diaphragm, is greater than 0.25 F andless than 0.37 F.
 3. A photogrammetric objective according to claim 1 inwhich the radii of curvature r of the lens surfaces, the lensthicknesses d, the air spaces l, the refractive indices for the heliumline nd, and the Abbe figures Nu d are substantially as set forth in thefollowing table: nd Nu d r1 +163,25 L1 d1 4,53 1,51680 64,2 r2 +74,41 l114,14 r3 +99,80 L2 d2 3,96 1,52054 69,7 r4 +53,18 l2 36,17 r5 +62,21 L3d3 26,82 1,74400 44,8 r6 +29,35 L4 d4 22,80 1,65100 41,9 r7 -55,22 L5 d56,80 1,59308 35,7 r8 +31,80 L6 d6 4,30 1,64350 47,8 r9 +926,20 l3 3,90r10 -1385,90 L7 d7 18,63 1,55232 63,5 r11 -22,00 L8 d8 3, 78 1,6363635,3 r12 +81,47 L9 d9 22,40 1,74300 33,3 r13 -58, 62 l4 22,91 r14 -48,76L10 d10 3,96 1,53172 48,8 r15 -83, 50 l5 22,29 r16 -51.42 L11 d11 10,301,64050 60,1 r17 -111,90 so'' 28,96
 4. A photogrammetric objectiveaccording to claim 1 in which the radii of curvature r of the lenssurfaces, the lens thicknesses d, the air spaces l, the refractiveindices for the helium line nd, and the Abbe figures Nu d aresubstantially as set forth in the following table: nd Nu d r1 +156,40 L1d1 3,80 1,51680 64,2 r2 +80,54 l1 15,20 r3 +113,70 L2 d2 3,80 1,5205469,7 r4 +55,43 l2 39,80 r5 +64,62 L3 d3 33,10 1,74400 44,8 r6 +28,07 L4d4 18,00 1,65100 42,2 r7 -53,06 L5 d5 4,70 1,59308 35,7 r8 +37,90 L6 d63,80 1,64328 48,0 r9 +833,00 l3 4,70 r10 -560,00 L7 d7 25,10 1,5687363,1 r11 -23,29 L8 d8 2, 35 1,63636 35,3 r12 +99,50 L9 d9 21,80 1,7430033,3 r13-66,80 l4 30,80 r14 -58,65 L10 d10 3,80 1,52542 64,7 r15 -99,50l5 26,50 r16 -58,10 L11 d11 4,70 1,52542 64,7 so'' 24,05
 5. Aphotogrammetric objective according to claim 1 in which the radii ofcurvature r of the lens surfaces, the lens thicknesses d, the air spacesl, the refractive indices for the helium line nd, and the Abbe figuresNu dare substantially as set forth in the following tables: nd Nu d r1+163,25 L1 d1 4,53 1,51680 64,2 r2 +74,41 l1 14,14 r3 +99,80 L2 d2 3,961,52054 69,7 r4 +53,18 l2 36,17 r5 +62,21 L3 d3 26,82 1,74400 44,8 r6+29,33 L4 d4 22,80 1,65100 41,9 r7 -55,22 L5 d5 6,80 1,59308 35,7 r8+32,50 L6 d6 3,00 1,64350 47,8 r9 973,65 l3 3,90 r10 -1385,90 L7 d718,00 1,55232 63,5 r11 -21,78 L8 d8 1,00 1, 63636 35,3 r12 +90,00 L9 d925,80 1,74300 33,3 r13 -57,55 l4 22,91 r14 -48,76 L10 d10 3,96 1,5337555,3 r15 -83,25 l5 21,00 r16 -51,42 L11 d11 10,30 1,64050 60,1 r17-111,90 so'' 30,8 F 100,0 F 100,0